Recording Roundtable Discussions

Recording roundtable-type discussions and interviews, as well as panel discussions, will stretch your abilities in ways that one-on-one interviews don’t. With roundtables, we have two main problems to overcome: keeping all of the participants on axis in relation to their microphones and avoiding excessive noise from having multiple microphones open at the same time.

For example, say we have four people at a table—three guests and one moderator. Usually, two people in conversation will be pretty routine—two mics, and we’re all set—but, as soon as there are three or more participants, things begin to get more difficult. By all means, try to avoid really large groups (I’m thinking of six or more people). In this case, the added noise floor can get very problematic, and the chances of phase cancellation become much higher. For this situation, thought should be given to a special type of microphone, known as the boundary mic, which is discussed below. So, for these reasons, let’s assume four people are to be recorded.

The first problem that we encounter in this situation is keeping everyone on axis when they are speaking. If there are only two people, situate them directly across from each other, so that they are looking straight at each other, with a microphone in front of each of them. When they speak, they will be speaking directly into the mic. However, with the example of four people, there will be someone who is sitting to the side of each participant. If we position the mic so that our subject directly faces the moderator, she will be on mic when addressing the moderator, but, if she wants to make a point to another panel member, her head will turn, and she will go off axis. I’ve battled this situation for years and have tried a number of possible solu tions: I have used lavalier microphones on the participants, but this only exag – gerates the problem, even though a lavalier microphone is usually omnidirectional. The change in perspective is quite noticeable, as is a shift in EQ as the head turns. With a body-mounted mic, there is always the chance of fabric noise as the mic rubs on the shirt or coat when the participant moves about, and so proper positioning is paramount in this case. Another problem with using a lavalier in this setting is that the participants all too often forget that they’re wearing it and will stand up at the end of the session, and either the mic ends up on the floor or it pulls the person back to the table. Most lavalier mics have the option of either being hard-wired with the mic cable or running wireless—be cognizant of radio-frequency interference if you’re running a wireless system; it can cause big problems, especially in an urban setting.

One thing that you should be aware of when recording roundtable discussions and interviews is phase cancellation owing to a number of microphones being live at the same time and the effect of direct to reflected sound arriving at any one microphone from various surfaces. When speakers are seated at a table, the mic not only picks up a direct sound from the speaker, but also a slightly delayed reflection from the tabletop, and then, slightly later still, a reflection from the walls, floor, and ceiling of the room. One of the best strategies that you can employ is to deaden the early reflection from the tabletop as best you can. Certainly, any kind of cloth covering will help (and will help muffle the sounds of pens being set down, papers being shuffled, coffee cups being moved, and so on), but even more sound absorption can easily be achieved by using carpet, instead of a tablecloth, or better yet, a table pad like many people use on their dining-room tables. Any kind of absorption that you can introduce to avoid the early reflections, as well as muffle any sounds of humans moving, will help you arrive at a clean, usable recording.

The problem of phase cancellation and sound colorization is one of the areas that we have to spend some time solving when doing roundtables. As I just mentioned, the time differential between direct sound and reflected sound can cause a very unnatural sound in the recording, and avoiding this can present quite a challenge. One option that I’ve had good results with in certain situations is the boundary or pressure-zone microphone (PZM). The design of this specialty mic produces a smooth pickup, regardless of the source distance from the mic—no off-mic sound, just a change in level. Integral to the microphone’s design is a fixed plate, above which the microphone capsule sits at a predetermined and fixed distance. Because sound strikes the mounting plate and then reflects back into the microphone capsule, the distance of reflected sound remains the same in all circumstances, and there is no colorization of the sound due to phase cancellation. Because of this design, the mic only picks up reflected sound from a set distance, and so there can be no off-axis sound in the recording. Although, in theory, this sounds like a wonderful solution, I’ve found that the sound of a well-positioned condenser microphone is preferable, if at all possible. However, for those times when we are faced with a large number of people at the table, or the requirement for a very unobtrusive microphone presence, the boundary mic can be an option worth investigating.

Crown Soundgrabber PZM

This type of microphone is available in cardioid, hyper-cardioid, omni, and stereo configurations. Although not ideal for critical recording situations, where the discussion or interview will be used for final release, I’ve had very good luck with these mics in a variety of situations, such as a large number of people sitting around the table or in the room, where individual microphones would be impractical. Also, I have participated in recording focus groups for a number of products, where the recording equipment (both video and audio) should be as invisible as possible, to bring out honest comments from the participants. In this case, I would place a couple of PZMs on the walls, ceiling, or floor, as the occasion warranted, and the participants were not aware that audio recording equipment was present. The comments could then be clearly heard and transcribed as needed.

Using a table-mounted omnidirectional mic helps with some of these problems, but I feel that it picks up too much of the room, as well as other participants’ speech. A cardioid is a nice balance and a good compromise. Earlier in this chapter, I discussed the Beyerdynamic M201, and I have had good success with that mic in this setting, even though it is a hyper-cardioid. I would recommend this only for those participants who are knowledgeable and experienced in the process of the multiperson interview or discussion, owing to the extremely tight pickup pattern of the microphone. In most instances, I recommend a cardioid pattern on a largediaphragm condenser mic for these situations. Because the roundtable is taking place in a controlled environment, instead of on a street or some other random place (such as would be the case with the one-on-one interview), a good-quality studio microphone would be appropriate in this situation and yields superior results. And don’t forget to use pop guards or windscreens to keep those nasty pops at bay!

Another problem often encountered in recording roundtable discussions is one of a participant striking the table as he makes a point. This is a very natural thing that most people do, but it can be extremely distracting when one listens to the recording. Along with those windscreens, make sure that the mics have proper and adequate shock mounting and isolation.

In this type of discussion, the participants will often have notes with them, and so paper rustle can be an issue. Here is a chance for you to practice your diplomacy to constantly remind them to be very careful when moving paper (a little more on this in a minute, as we talk about mixing strategies for roundtables). Also, if you have a clear line of sight into the studio and can capture the attention of either the offending individual or the moderator, you can use hand signals to warn of the noise problem that you’re having. If you are in a studio situation when recording roundtable discussions, you should consider setting up a cue feed to the moderator, so that you can use the cue as a communications link to quietly mention the problem, and the moderator can signal the offender. Setting up a cue feed for communication purposes is always a good idea when doing this type of recording, so that you can alert the moderator that you’re going to have to pause the recording in 5 minutes, or whatever the case may be.

Atlas Desk Stand Setup

I think that the least intrusive method of placing the mics is to use desk stands. Using mic stands and booms takes up too much room for four or more people, and they just get in the way; you want to make your amateur guests at ease, so avoid large stands if you can. Also, you should be aware that a large-diaphragm condenser mic can be quite heavy, so make sure that the desk stand that you select can support the weight of the mic without tipping over.

Tom Blakemore has been an active audio engineer for over thirty years, working in film, television, commercial, and corporate communications as a supervising sound editor and mixer. His film work includes Emmy Award winning documentaries, Academy Award nominees, Directors Guild of America Best Documentary winners, and Audience Award winners at the Toronto, Chicago and Amsterdam Film Festivals. Tom lives in Chicago, where he is an adjunct professor at Tribeca Flashpoint Media Arts Academy teaching film sound, and is a member of the Motion Picture Sound Editors (MPSE) and the Audio Engineering Society (AES).

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